Caption: Afinitor chemotherapy tablet. Afinitor contains the substance Everolimus. Everolimus is a signal transduction inhibitor, a substance which blocks certain signals within cells that make them grow and divide. Everolimus inhibits a protein called mTOR (mammalian target of rapamycin) which controls other proteins that trigger cancer cells to proliferate. It is used to treat advanced kidney cancer, and certain kinds of pancreatic, brain and breast tumours.